1. Field of the Invention
The invention relates to a device for detecting faulting firing in an internal-combustion engine, having a respective pressure sensor assigned to each cylinder for emitting a pressure signal corresponding to the combustion-chamber pressure, a position sensor generating at least one crankshaft signal and camshaft signal at a particular piston position, and an evaluation section determining faulty firing of a cylinder from the pressure signal and the crankshaft position signal.
Such a device is known, for example, from German Published, Non-Prosecuted Application DE 32 12 669 A1. In that case, the combustion-chamber pressure is measured by means of a pressure sensor during two time intervals after the top dead center of a cylinder. The first time interval corresponds approximately to the duration of the firing process and the second time interval follows thereafter. The measuring signals of the pressure sensor are compared with predetermined threshold values in each case during the two time intervals. An observation of whether the respective threshold value is reached or not allows a statement to be made concerning the pressure variation, by means of which it is possible to distinguish between proper firing and faulty firing and even misfiring.
However, aging, temperature effects, errors in signal conditioning etc., in such a case can cause drift effects to occur in the case of the signal from the pressure sensor. As a result, the reliability of evaluation becomes less and less over time. In an extreme case, the pressure sensor may even fail completely and no longer supply any signal at all. In that case the known device would wrongly detect misfiring instead of the failure of the pressure sensor.